Incident Chronology at Peach Bottom Atomic Power Plant: 1974- 2012

$285,000 in fines for the improper insulation of safety system

relief valves at Unit 3. Company spokesman Neil McDermott admitted

there is "absolutely no question and we readily admit that the insulation

was improperly installed" (Patriot News, February 25, 1992.)
March 6, 1992 - The NRC observed: "Several weaknesses were

noted in the training program during the conduct of the examinations.

Differences between Peach Bottom and Limerick had a negative impact on

some LSRO lesson plans in that the lesson plans did not track actual plant

practice. LSRO responsibilities were not well defined at Limerick and differ

from those at Peach Bottom. Training was not always given as described in

the task to training matrix or the qualification manual. In general, the

candidates' knowledge of the site and plant at which they were not

normally stationed was weak." (Lee H. Bettenhausen, Chief, Operations

Branch, Division of Reactor Safety.)

deficiencies in their primary containment isolation systems.(NRC

inspections 50-277/92-07 and 50-278/92-07.) (See December 16, 1991

for related incident.)

Team (IPAT) observed, "an operator exit the fourth floor administration

building radiological control point...without properly surveying personal

articles being removed from the radiological control area" (NRC Region I

IPAT 50-277/92-80 and 50-278/92-80.)
March 13, 1992 - Philadelphia Electric "discovered" Unit 2 residual

heat removal equipment valves were not installed."With the check valves

on the discharge of the sump pumps for the 'B' and 'D' RHR rooms not

installed, this design basis can not be met. Specifically, during a loss of

coolant accident, concurrent with a loss of off-site power, the reactor

building sump pumps would not be available due to the loss of off-site

power" (NRC inspections 50-277/92-07 and 50-278/92-07.)
March 16, 1992 - Due to a turbine exhaust drain line valve failure,

the Unit 2 high pressure coolant injection system was rendered

inoperable.(NRC inspections 50-277/92-07 and 50-278/92-07.) (See

March 23, 1992 for related incident.)

when the turbine overspeed trip device did not reset during testing" (NRC

inspections 50-277/92-07 and 50-278/92-07.) (See March 16, 1992 for

related incident.)

instrumentation associated with the 2B reactor water level reference leg

condensing chamber inoperable" (NRC IR 50-277/92-13 and 50-278/92-

13.) (See September 11, 1990, March 27, 1992 and July 26, 1992 for

related incidents.)
March 27, 1992 - Unit 2 was shutdown due to inoperable reactor

level instrumentation. (See September 11, 1990, March 26, 1992 and

July 26, 1992 for related incidents.)
April 2, 1992 - A settlement was announced on the two lawsuits

brought against PECO by Peach Bottom's co-owners: Public Service Electric

and Gas Company, Delmarva Power and Light Company and Atlantic City

Electric Company. The suits were related to the NRC shutdown of Peach

Bottom on March 31, 1987."As part of the settlement, Philadelphia

Electric will pay $130,985,000 on October 1, 1992 to resolve all

pending litigation." (Joseph Paquette, April 8, 1982.) (See July 27,

1988 for background material.)

about 100% power. "The shutdown was required because a one inch vent

line failed at a welded connection on the condensate supply herder to the

offgas recombiner condenser...A reactor scram and primary containment

isolation system (PCIS) group II and III occurred" (NRC IR 50-277/92-09

and 50-278/92-09.)

following infractions: "Contrary to the above requirements, the ODCM

[Offsite Dose Calculation Manual] specified composite water sampler at the

intake had been inoperable during the period August 30, 1991 to March

19, 1992, and the specified composite water sampler at the discharge had

been inoperable since August 8, 1991 and remains inoperable at the time

this inspection [was] conducted March 23-27, 1992. The licensee's efforts

to complete corrective action prior to the next sampling period were

ineffective" (NRC inspections 50-277/92-08 and 50-278/92-08.)
April 29, 1992 - A Health Physics technician was contaminated

in the de-watering facility when "contamination controls were

compromised. According to the licensee's investigation, a defective latch

and hinge on the fill-head access door allowed contamination to escape

from the liner to the room during processing. Contamination levels on

near-by radwaste equipment were as high as 200 mrad/hour. The

general area surfaces in the truck bay were contaminated up to 30,000

dpm/100cm (2)" (NRC IR 50-277/92-12 and 50-278/92-12.)

[at Unit 3] in order to repair a large steam leak through a manway on the

'F' moisture separator tank" (NRC inspections 50-277/92-11 and 50-

278/92-11.)

power.(See June 27, July 23, July 26 and July 27, 1992 for related

incidents.)
May 15, 1992 - PECO initiated a shutdown of Unit 2 "due to

inoperability of the high pressure coolant injection and the reactor core

isolation cooling systems" (NRC inspections 50-277/92-11 and 50-278/92-

11.) (See June 25, 1992 for related incident.)

trip due to a malfunctioning combined intermediate valve.

pump failed and was declared inoperable.

1992 were $0.33 per share, $0.25 lower than the $0.58 per share

earnings for the corresponding period last year. The reduction in earnings

was primarily the result of the previously reported settlement of litigation

by the co-owners of Peach Bottom Atomic Power Station which reduced

first quarter earnings by approximately $0.27 per share" (J.F. Paquette,

Jr., Chairman of the Board and Chief Executive Officer, Report to

Shareholders First Quarter, 1992).

was declared inoperable "due to excessive water buildup in the turbine

casing" (NRC IR 50-277/92-13 and 50-278/92-13.) (See May 15, 1992 for

a related incident.)

May 12, July 23, July 26 and 27, 1992 for related incidents.)

explosion at the #1 transformer station. Units 2 and 3 were operating at

at, or around, 95 % power. As a result of the explosion, Unit 3 scrammed

and there were several emergency safeguard actuations.(See May 2, 1991

for a related incident.)
July 14, 1992 - "Unit 3 was manually scrammed from 63% power

due to a decreasing main condenser vacuum" (NRC IR50-277/92-13 and

50-278/92-13.)
July 17, 1992 - Unit 2 experienced a turbine trip and reactor

scram at 95% power during a severe lightning storm.

power.(See May 12, June 27, July 26 and July 27, 1992 for related

incidents.)
July 25, 1992 - "Unit 2 was shutdown due to a safety relief valve

bellows rupture alarm" (NRC IR 50-277/92-13 and 50-278/92-13.)

May 12, June 27, July 23 and July 27, 1992 for related incidents.)

American nuclear reactors may be defective according to the NRC.

"Engineers are concerned that in a serious accident involving the rapid

loss of coolant and pressure from the reactor, the device would give a false

reading, indicating the reactor core was still covered with water when it

actually was not and therefore in danger of melting down" ( Sunday

Patriot News, July 26, 1992 A3.) (See September 11, 1990 and March 26

and 27, 1992 for related incidents.)

Peach Bottom has had a history of problems in this area.

" In August 1990, the licensee identified that the Unit 2 level

instrumentation served by the 2B condensing chamber and reference leg

was indicating values about 11 inches higher than similar instruments

served by the 2A condensing chamber...They [PECO] concluded that the

actuation set points for several safety systems would be exceeded during

transients or accidents, declared the instruments inoperable and

completed a plant shutdown. Following the 1990 event, the licensee

revised the channel check procedures to provide better monitoring and

evaluation of the instruments...A second level offset event, again

involving the Unit 2B condensing chamber, occurred in March 1992. The

improved surveillance procedures helped the licensee identify the offset

before it had exceeded 3 inches. In response, the licensee established a 4

1/2 inch offset operability limit, and closely monitored the

instrumentation..." (NRC IR 50-277/92-16 and 50-278/92-16.) ( For

related incidents see September 11, 1990 and March 26-27, 1992.)
July 27, 1992 - The 'A' recirculation pump tripped at Unit 2.

(See May 12, June 27, July 23 and July 26, 1992 for related

incidents.)
July 27, 1992 - Peach Bottom and 86 other suspected nuclear

reactors "depend on a defective and dangerous fire-barrier system

to protect electrical cables used for a safe shutdown during a

fire/accident." (Nuclear Information and Resource Service (NIRS), July

27, 1992.) The company who produces the Thermo-Lag 330 system is

Thermal Science, Inc. (TSI), St. Louis, Missouri. Among the problems with

Thermo-Lag are: combustibility, toxicity, seismic qualification,

vulnerability to water, incomplete installation and ampacity calculation

errors.

In an IR issued on September 10, 1992, PECO requested a temporary

NRC observed: "...the licensee could not post the required fire watch for

residual heat removal system cables running through the Unit 3 offgas

pipe tunnel because it is a high radiation area".

(NRC IR 5 277/92\16 and 50-278/92-16.)
August 6, 1992 - The NRC issued a violation "for operation of the

reactor cleanup system in a mode not established in approved operating

procedures, is of concern because it represents a weakness in your control

of operating activities" (NRC IR 50-277/92-13 and 50-278/92-13.)

the E-4 emergency diesel generator.

Unit 2 due to improper blocking. PECO "determined that the generator

lock-out occurred because the permit being applied in the South Substation

was incorrect" (NRC IR 50-277/92-16 and 50-278/92-16.)

supply failed. The root cause was a failed topaz inverter.

marijuana use.

security, one unresolved Fitness-for-Duty(FFD) item was identified. The

NRC also cautioned that "... additional attention is warranted on the

effectiveness of routine security patrols since we identified certain

deficiencies during this inspection that should have been identified by

your officers on patrol" (NRC IR 50-277/92-20 and 50-278/92-20.)

injection (HPCI) system initiated: "... Unit 3 experienced a primary

containment isolation system (PCIS) group I isolation on main steam line

(MSL) low pressure. This resulted in closure of the MSIVs and a reactor

scram. During the post-scram pressure and level transient, vessel water

decreased to the ECCS Lo Level initiation setpoint. The high pressure

coolant injection (HPCI) and reactor core isolation cooling (RCIC) systems

initiated and injected into the reactor vessel. The alternate rod insertion

and reactor recirculation point trip logic also actuated. Three main steam

safety relief valves (SRV) opened automatically for a short period to

control pressure, and later re-closed. The licensee declared an unusual

event (UE) at about 9:25 p.m. due to the initiation and ejection of an

ECCS system in response to a valid signal...At about 11;16 p.m., while

proceeding with the plant cooldown, reactor vessel level increased above

the normal operating band and caused a HPCI and RCIC high reactor

vessel water level turbine trip. Due to the temporary loss of HPCI as a

means of pressure control, reactor pressure increased to the high pressure

scram setpoint. the operators manually operated an SRV to reduce

pressure, and restarted HPCI and RCIC. the licensee also reported this

second scram signal to the NRC via the ENS. All systems responded as

expected following the PCIS group I isolation and reactor scram, and the

subsequent high reactor pressure scram" (NRC IR 50-277/92-27 and 50-

278/92-27.)

PECO management decided to shut the plant for five days.

After reviewing the events the NRC issued a Notice of Violation and

criticized, "The control room staff did not effectively monitor developing

reactor coolant stratification following the Unit 3 automatic scram, and

certain Technical Specification reactor pressure/temperature limits were

exceeded. Adequate controls were not in place to ensure that the transient

was appropriately evaluated before plant restart. Also, operators did not

record required pressure data used to evaluate compliance with

pressure/temperature limits following a Unit 2 shut-down." (E.

Wenzinger, Chief, Projects Branch 2, Division of Reactor Projects,

November 16, 1992.)

reactor operators (SRO) examinations:"Since SRO Upgrades are currently

licensed individuals at your facility, we are concerned that your training

program may not be emphasizing a high level of performance among

reactor operators in referring to and using procedures" (NRC IR 50-

277/92-18 and 50-278/92-18.)

“there was a significant cool down in the bottom head as a result of the loss of

forced circulation” (IR 50-277/94-04 and 50-278/94-04.)
October 16, 1992 - The NRC identified programmatic weaknesses related

to the System Manager program. (NRC IR 50-277/92-26 and 50-278/92-26.)

which involved the potential for loss of power in the drywell...had not yet been

resolved and warrants your attention” (NRC IR 50-277/92-30 and 50-278/92-

30.) (See December 12, 1995 for a related incident.)

dilution (CAD) system gas analyzer occurred at Unit-2. On both occasions PECO

personnel did not “understand” or “recognize” the problem with the CAD. (NRC

IR 50-277/92-29 and 50-278/92-29.)

Initial SALP of Licensee Performance “including numerous component failures,

lapses in the operating procedure and deficiencies in engineering and technical

support” (York Daily Record, January 9, 1993.) “Among the areas identified for

improvement were plant performance monitoring and engineering and

technical support” (PECO, Report to the Shar eholde r s, March 1, 1993.)

failed. (NRC IR 50-277/92-32 and 50-278/92-32.) (See March 2, 1993 for a

related incident.)
December 17, 1992 - Turbine control oscillations occurred while Unit-2

was operating at 89.5% power. The plant was “stabilized” at 76.5% power. (NRC

IR 50-277/92-32 and 50-278/92-32.)
December 19, 1992 - An Unusual Event was declared “due to a loss of

emergency communications capabilities. Both units were operating at 20%

power” (NRC IR 50-277/92-32 and 50-278/92-32.)
January 1, 1993 - The Unit-2 high pressure coolant injection system was

declared inoperable. (NRC IR 50-277/92-32 and 50-278/92-32.) (See January

25 and 31, March 1 and August 9, 1993, for related incidents.)- January 21, 1993 - A Notice of Violation (NOV) was issued relating to the

NRC’s Motor-Operated Valve (MOV) Inspection on October 19-23 and November

3, 1992. PECO “1) did not document nonconforming positions, 2) did not

properly disposition existing nonconforming conditions, and 3) did not take

timely corrective actions to evaluate and resolve nonconforming conditions in

MOVs...” (NRC IR 50-277/92-82; 50-278/92-82.) (See August 8-16, 1998, for a

related incident.)
January 25, 1993 - During surveillance testing, the Unit-3 high

pressure coolant injection system was declared inoperable. (NRC IR 50-277/93-

01 and 50-278/93-01.) (See January 1 and 31, March 1 and August 9, 1993, for

related incidents.)

was declared inoperable. (NRC IR 50-277/93-01 and 50-278/93-01.) (See

January 1 and 25, March 1, and August 9, 1993, for related incidents.)
March 2, 1993 - Unit-2 scrammed while operating at 70% reactor power.

(NRC IR 50-277/93-03 and 50-278/93-03.)

condensate pump tripped while the Unit was operating at 100% power” (NRC IR

50-277/93-03 and 50-278/93-03.) (See December 7, 1992 for a related

i n c i d e n t . )

declared inoperable. (NRC IR 50-277/93-03 and 50-278/93-01.) (See January

1, 25 and 31 and August 9, 1993 for related incidents.)
March 7, 1993 - [R]eactor scram, due to a low reactor vessel level.

Reactor feed pump trip while lowering reactor power to with in bypass valve

capacity, to allow work on turbine valves” (IR 50-277/94-04 and 50-278/94-

0 4 . )
March 10, 1993 - During a radiological safety inspection (February 8-9,

1993 and March 1-2, 1993), relating to a “breakdown of personnel access

controls associated with the Transversing In-core Probe (TIP), the NRC found:

“...control of personnel during such operations is considered very important as

the TIPs represent one of the higher radiation sources that personnel have a

potential for encountering” (NRC IR 50-277/93-02; 50-278/93-02.) (For related

incidents see June 22 and 25, September 24, October 4, and November 11,

1993; June 19 and November 29, 1994 and August 24, 1995.)

March 23, 1993 - High oxygen concentration was found in Unit- 2

containment during power operation. (NRC IR 50-277/93-03 and 50-278/93-

03.) (See January 17, 1992 for a related incident.)- April 24, 1993 - Unit-2 was manually scrammed “following declaration

of all reactor vessel level instrumentation served by the ‘2B’ condensing

chamber inoperable” (NRC IR 50-277/93-06 and 50-278/93-06.) (See related

incident on March 27 and July 26, 1992 and September 22, 1993.)
April 30, 1993 - A Notice of Violation was issued following an an NRC

inspection of the electrical distribution system. Other design and operational

weaknesses were identified relating to the emergency diesel generator. (NRC IR

50-277/93-80 and 50-278/93-80.) (See July 17, 1995 for a related

d e v e l o pme n t . )
May 26, 1993 - Three individuals were found to be “inattentive” or

“sleeping.” (C. Anderson, NRC Region I.)

not fully effective in that a higher than expected dose rate was identified upon

the entry” (IR 50-277/94-04 and 50-278/94-04.) (See March 10, June 25,

September 24 and October 4 and November 11, 1993 and January 19 and

November 29, 1994.)
June 24, 1993 - PECO discovered a “mispositioned” control rod at Unit-2.

The reactor was operating at 60% power. (NRC IR 50-277/93-15 and 50-

278/93-15.) (For related events see February 22, 1994, April 21, 1995 and

February 15, 1997.)

04 and 50-278/94-04.) (See March 10, June 22, July 22, September 24,

October 4 and November 11,1993 and January 19 and November 29, 1994.)
July 4, 1993 - Unit 3 was shutdown. “An unplanned Unit 3 mid-cycle

outage began on July 6, 1993, to replace to known leaking fuel bundles.” A fuel

leak was detected in May 1992. (NRC IR 50-277/93-15 and 50-278/93-15.)
July 30, 1993 - Unit-3 was manually scrammed “after a loss of

condenser vacuum” (NRC IR 50-277/93-15 and 50-278/93-15.)

inoperable (NRC IR 50-277/93-17 and 50-278/93-17.) (For related incidents

see, January 1, 25 and 31 and March 1, 1993.)
August 11, 1993 - Unit-2 was manually scrammed. (NRC IR 50-277/93-

17 and 50-278/93-17.)

pumps were deemed inoperable. The plant was operating at 100% power. (NRC

IR 50-277/93-17 and 50-278/93-17.)- September 14, 1993 - The reactor feed pump tripped due to “flow

oscillations” at Unit-3.

preparedness program on June 28-30, 1993 found: “Significant areas for

potential improvement included wind direction information use by emergency

response groups, event announcements in the Emergency Operations Facility by

the ERM [Emergency Response Manager], and ERM recognition of the best

indication of main stack radiation” (NRC IR 50-277/93-10; 50-278/93-10.)